As the present trend in tire-making technology continues toward the use of higher silica loadings in rubber compounds, there is a challenge to contain levels of environmentally released volatile organic compounds (VOC), especially alcohol, during compounding, processing, cure and storage of silica-reinforced rubbers.
In our U.S. patent application Ser. No. 11/387,569, filed Mar. 23, 2006, the entire disclosure of which is hereby incorporated by reference, we described the preparation of alkyl alkoxy-modified silsesquioxane (alkyl AMS) compounds and alkyl/mercaptan co-alkoxy-modified silsesquioxane (alkyl/mercaptan co-AMS) compounds that generate less alcohol than conventional alkoxysilane-containing silica-coupling and/or silica dispersing agents used in rubber compounding. It was found that the decreased amount of alcohol produced when using the alkyl AMS and alkyl/mercaptan co-AMS compounds in rubber compositions resulted in vulcanized rubber compounds having one or more improved properties such as, but not limited to, enhanced rubber reinforcement, increased polymer-filler interaction and lower compound viscosity, providing for tires having improved wet and snow traction, lower rolling resistance, increased rebound and decreased hysteresis.
In the aforementioned patent application, we described AMS and co-AMS compounds that can be made by subjecting one or more trialkoxysilanes to hydrolysis and condensation in an aqueous alcohol solution in the presence of a hydrolysis and condensation catalyst such as, but not limited to, a strong acid (e.g., hydrochloric acid, sulfuric acid, phosphoric acid, and the like), a strong base (e.g., sodium hydroxide, potassium hydroxide, lithium hydroxide, and the like), a strong organic acid, and a strong organic base (e.g. hindered amine bases, guanidines, and the like). However, at the time of filing the above-referenced patent application, it was unknown how to produce similar AMS compounds that also contained amino groups, i.e., an amino AMS, an amino/mercaptan co-AMS, and an amino/blocked mercaptan co-AMS, because of special problems that might be encountered when using strong acids, strong organic acids, strong bases and strong organic bases as hydrolysis and condensation catalysts. It was also unknown what effects the addition of such amino AMS and/or amino co-AMS compounds to rubber compounds would have on the properties of such rubber compounds and components of tires containing the rubber compounds.